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| Titel |
Assessment of the ‘CO2 fertilization effect' on crops with the AquaCrop model |
| VerfasserIn |
Eline Vanuytrecht, Dirk Raes |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250050795
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| Zusammenfassung |
| The global climate is changing due to the augmented emission of greenhouse gases. Elevated
air temperatures, increased evaporative demand of the atmosphere and altered rainfall
patterns are expected and may have a detrimental impact on crop growth and production.
In contrast, the steady increase of the atmospheric CO2 concentration ([CO2]),
which is a main cause of the climatic changes, can have a positive effect on crop
productivity and water use (‘CO2 fertilization effect’). The combined impact of climatic
changes and elevated [CO2] on agricultural productivity can be evaluated with
models.
AquaCrop, the crop water productivity model of FAO is widely applicable for a broad
range of crops and geographical locations, and aims for accuracy, robustness and simplicity
(Raes et al., 2009; Steduto et al., 2009). In the model, crop transpiration and crop water
productivity responses to elevated [CO2] are simulated through a downward adjustment of
the crop transpiration coefficient and an upward adjustment of the water productivity
parameter (WP). Evidence for both effects was obtained via a meta-analysis of primary
literature on FACE (free air CO2 enrichment) experiments. The procedure to consider the
effect of CO2 was recently adjusted because the existing procedure for adjustment of
WP (Steduto et al., 2007) resulted in a strong overestimation of the crop response
when compared to FACE experiments. The lower response in the field can be due
to suboptimal fertility management that does not consider the increased nitrogen
demand under elevated [CO2], crops’ limited sink capacity, and carbon leakage
processes.
With the updated procedure, users are now allowed to specify their preference to simulate
the CO2 effect to be closer to the lower ‘field’ effect or the higher ‘theoretical’ effect as
derived by Steduto et al. (2007). This feature permits to differentiate between crops with
different sink capacities (e.g., potato with a higher sink capacity than wheat) or to
follow trends in breeding (e.g., improved varieties might exhibit a more optimal
response to CO2 in the future). Further, the updated procedure treats C3 and C4 crops
differently as the positive CO2 effect on C4 crops is mainly confined to decreased crop
transpiration.
AquaCrop can be run with weather data projected for the future as generated by
(stochastic) weather generators in combination with projected [CO2] levels for different
climate scenarios to assess crop production and the soil water balance under future climatic
conditions. A number of simulation studies have demonstrated that the ‘CO2 fertilization
effect’ can temper the detrimental effects of changed climatic factors in certain locations or
improve the agricultural production in other places. For a case study in Tunis (Tunisia),
simulated yield of wheat decreased for the period 2046-2065 compared to the baseline period
if only the effect of climatic changes (rainfall, ETo and temperature) were considered while
yield increased if also the effect of elevated CO2 was considered. For another study
in Mekelle (Ethiopia), simulated yield of tef increased modestly under changed
climatic conditions for the period 2046-2065 compared to the baseline period without
consideration of elevated [CO2]. If the ‘CO2 fertilization effect’ was considered, the
yield increase was even much stronger. The simulation results confirm the need for
quantification of the CO2 effect on crops in addition to the effect of altered air temperatures,
rainfall patterns and evaporative demand to assess the agricultural productivity in the
future.
References
Raes, D., Steduto, P., Hsiao, T.C., Fereres, E., 2009. Agron. J. 101, 438-447.
Steduto, P., Hsiao, T. C., Raes, D., Fereres, E., 2009. Agron. J. 101, 426-437.
Steduto, P., Hsiao, T.C., Fereres, E., 2007. Irrig. Sci. 25, 189-207. |
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